Fuel cell technology moves closer to commercial viability with the announcement by power generation group Siemens that it has reached a milestone in its development of low-temperature fuel cells.
In tests at the company’s Erlangen laboratory its polymer electrolyte-membrane (PEM) fuel cell has clocked up 1,500 hours fault-free running. It has a maximum output of 50kW and is destined for use in vehicles ranging from buses to submarines.
Siemens has pencilled in a 2000 date for the first PEM-fuelled buses to appear on the streets. It is now building such a bus in partnership with MAN and energy storage equipment supplier Lende. At about the same time, a PEM fuel cell will be installed in new German submarines.
The PEM cell, which operates at 70-80iC, is less energy efficient than the alternative high-temperature solid oxide fuel cell being developed for use in small power stations.
The solid oxide cell, operating at 700-800iC, would be unsuitable for use in vehicles because of the high working temperature but makes economic sense for generators, which will be able to recover much of the heat for local heating needs.
Fuel cells work by converting chemical energy into electricity and heat.
An electric current is produced by creating, in effect, a difference in electrical pressure inside different parts of the cell. This causes the current to flow through electrolytic fluid in the cell. The pressure differential, or voltage, occurs when hydrogen gas atoms, which try to migrate through the cell, are prevented from doing so by tiny holes in the membrane structure.